I used a set of Posies Dual-flex springs on the front of my 55.1.
It lowered the truck slightly (27.5" tall at the wheel well).
In the back, I removed leaf #6.(29" tall at the wheel well)
My tires are 21575R15.
The ride is great.
I don't know how much this is lower than stock, maybe someone has stock springs in good condition and could measure it for us.

regards,
Leon